In previous threads it has been suggested that setting each character to follow themselves (e. g. Cassandra to follow Cassandra) makes the hold position instruction more reliable. I have found this useful, and also using the tactical view and individually setting character positions (left double click on PC, can't help with consoles) is fairly reliable. If the controlled character moves too far away then followers are likely to close up, so fighters using Bulls Charge (? not sure of exact name) are likely to break the "hold position" effect. Fade step doesn't seem to go so far, so is less of a problem.